Demonstrated Treatment

Technologies

Stewart Abrams, PE

Langan Engineering and Environmental Services, Inc.

Learning Objectives

What we will learn:

What technologies are commercial and available now for the treatment of PFAS in both soil and water?

What developing technologies exist that may be available in the future?

What are the key features of each technology?

What are the advantages/disadvantages and limitations of each technology?

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PFAS Treatment Technologies

ITRC Defined Three Categories:

Field Implemented Technologies – Technologies that have been demonstrated under full-scale conditions at multiple sites, by multiple practitioners and multiple applications are well documented in peer-reviewed literature

Limited Application Technologies – Technologies that have been implemented on a limited number of sites, by a limited number of practitioners, and may not have been documented in peer-reviewed literature.

Developing Technologies – Technologies that have been researched at the laboratory or bench scale, but these technologies have not been field demonstrated.

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Water Treatment Effective conventional approaches, with limitations:

Carbon adsorption

Resin adsorption

Reverse osmosis

Typically ineffective conventional technologies: Air stripping, air sparging

Technologies in development: Examples include - bioremediation, chemical oxidation, chemical

reduction, thermal desorption, electrochemical, others

Be aware of precursor transformations via treatment

processes, particularly with oxidation and biodegradation

Treatment objectives can drive the decision making

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Activated Carbon Granular Activated Carbon (GAC)

most widely used technology.

GAC performance varies based on site-specific conditions, carbon source types and manufacturing methods.

Shorter-chain PFAS break through faster than longer chain, but generally still within the range considered feasible.

GAC less effective for PFCAs than PFSAs of same C-F chain length.

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Photo used with permission: Calgon Carbon Corporation, 2018

Typical GAC Process Diagram

Influent GAC vessel “Lead”

Second GAC vessel “Lag”

Monitoring Influent

Mid-point

Effluent

Carbon Change Out Lead to reactivation

Lag to lead

New to lag

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EBCT – Empty bed contact time

Diagram used with permission: Calgon Carbon Corporation, 2018

Reactivated Carbon

GAC can be “reactivated” under high temperature and reused.

Less aggressive “regeneration” methods are not appropriate for PFAS.

Contract reactivation services provided by most GAC suppliers (e.g., round trip service).

Reactivated carbon typically used in wastewater and groundwater remediation applications.

For drinking water applications, reactivated carbon should be used with caution to avoid commingling with carbon from other sources. Must comply with AWWA B605-13 Reactivation of Granular Activated Carbon standard.

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GAC Testing Isotherm Testing

Batch test to evaluate GAC adsorptive capacity

Rapid Small-Scale Column Tests (RSSCT) Simulates full-scale performance in short

period of time

Small diameter (less 1.0 cm ID) are typical

Identifies carbon type, breakthrough data, usage rates

Can be used to calibrate vendor models

Pilot testing When water quality variability or

combinations of processes are necessary.

Column treatment study

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Photo courtesy of Langan Engineering

Isotherm Testing

Not a dynamic indicator of full scale performance

Provides screening-level understanding of effectiveness

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Graphics used with permission: Calgon Carbon Corporation, 2018

Solution in contact with increasing amount of carbon

Equilibrium Reached

Column Testing Example

Less effective for shorter chain carbon compounds (PFBS and PFHxA).

Differences between sulfonates and carboxylates.

Initial breakthrough above detection: PFBS at 256 days.

PFHxA at 311 days.

PFHpA at 367 days.

0

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4

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0 200 400 600 800 1,000 1,200P

FA

S C

on

cen

trati

on

, n

g/L

Simulated Days of Operation

PFBSPFBS Average InfluentPFHpAPFHpA Average Influent

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Graph courtesy of Langan, with permission of client.

Ion Exchange (IX) Resin vs. GAC

GAC removes by adsorption

using hydrophobic “Tail”

PFOS – Perfluorooctane Sulfonate

Selective IX Resins removes by both ion exchange

and adsorption using both “Head” & “Tail”

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Figure Courtesy of Langan/Adapted from Purolite

Sulfonate group

Hydrophobic “Tail” Ionized “Head”

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Single-Use Selective Resin + Incineration

Short Contact Time ~3 minsSimple & Effective - Operator Preferred

Incineration or other disposal alternative

Treated waterPFAS in water

Illustrations courtesy of Purolite, Inc.

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Single-Use Selective Resin Simple, field-demonstrated

High removal effectiveness

Small footprint/headspace

High operating capacity 100,000 to 350,000 BV

Operation costs Need to be based upon site-

specific resin usage rates and disposal costs

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Example Ion Exchange Removal Curves at Specific Influent Concentrations

Data courtesy of Purolite, Inc.

Precautions in Reviewing Data Compare apples to apples

Empty bed contact time (ECBT)

• GAC EBCT for this study is half of what is typically (10-12 min) used

• IX EBCT is shorter (2-3 min)

Compare gallons treated before breakthrough, the difference between GAC and IX may be less pronounced

Factors that impact effectiveness

• Site specific geochemical parameters

• Co-contaminants

• Other factors

Consider site-specific testing before selecting sorptive media

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Data courtesy of Purolite, Inc.

Regenerable Ion Exchange Resins

Demonstrated on the bench to be equally effective after multiple regeneration cycles

Regeneration solution is solvent and brine

Solvent can be recovered and reused

Distilled brine runs through GAC then is loaded on high-capacity IX media for incineration

The low volume, high concentration liquid waste may in the future be able to be destroyed with destructive options (developing technologies such as non-thermal plasma, electrochemical oxidation)

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Regenerable Resin Process

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PFAS

Image provided courtesy of ECT2 and Wood

In Situ Sorption Colloidal activated carbon with a biopolymer

Technology widely demonstrated for VOCs

Can be installed as a treatment barrier

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Before Treatment

Treatment zone with 20 inj points

30 Months After Injection

Graphics used with permission of Regenesis, Inc., after: Rick McGregor, Remediation, 2018; 28:33-41

Full-scale demonstrations at several sites

Unknown longevity, but modeling predicts >100 years

Reverse Osmosis

Membrane Processes

Effective for PFAS High pressure membrane

High energy usage

Reject water disposal

Typically used on lower flow rates

Questions about sustainability

Removes a wide range of constituents: Including hardness, dissolved solids, as well as VOCs and PFAS

Costly Capital

Operating

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Flocculation/Coagulation

Pre-treatment technology Many products have been tested:

Alum, ferrate, ferric sulfate, Polydiallyldimethylammonium chloride (polyDADMAC)

Multiple flocculants can be used to address varied chain lengths

Pilot-scale systems in Europe Sludge disposal is needed Carbon or Resin Polishing

Results in less disposal quantities than GAC directly

Non-detect concentrations with adsorbent polishing

Photos courtesy of Bill DiGuiseppi, Jacobs

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Soil Remediation Technologies

Conventional Excavation and landfill

Excavation and offsite incineration

Stabilization

Developing/Limited demonstrations Soil Washing

Thermal

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Soil Remedial Technologies

Excavation with offsite disposal in a permitted landfill, where allowed. Out of abundance of caution, some

landfills no longer will accept PFAS soils. Do not assume this is straightforward.

Excavation with offsite incineration Must be >1,100oC for PFAS

Destruction assumed but not well documented

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Photo courtesy of CH2M/Jacobs

Soil Remediation Technology Stabilization/Immobilization

via sorption Combination of powder-

based reagents with high surface area and various binding methods: Powdered activated carbon,

aluminum hydroxide, kaolin clay Added from 1-5% by weight to soil Fully commercial & demonstrated

in Australia Extensive testing, research and

demonstration in Europe

Images courtesy of Ziltek™ and AquaBlok Ltd.

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Treatability Study: PFOS/PFOA in Soil Two commercial airport sites in Australia

Site soils mixed with proprietary combination of GAC and additives at various addition rates

Soil leachates prepared using the Toxicity Characteristic Leaching Procedure (TCLP)

Data courtesy of Ziltek Pty Ltd.

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Soil Stabilization Example

Photos and information courtesy of Ziltek Pty Ltd.Cell design graphic courtesy of Langan

1,100 tons PFAS impacted soils stabilized on-site at two airports during upgrade activities.

Transport and disposal in a purpose-built burial cell located at a municipal waste landfill site.

Cell lined and covered with stabilization agent.

EPA Test Method 1311 and 1320 (TCLP and MEP) to verify performance.

Soil Burial Cell Design

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Developing - Treatment TechnologiesStewart Abrams, PE

Langan Engineering and Environmental Services, Inc.

Developing Separation Technologies Zeolites

Microporous aluminosilicate minerals

Limited testing beyond PFOS/PFOA

Less sorptive than GAC

Requires disposal/destruction of media

Foam Fractionation Air microbubbles separate PFAS

Demonstrated in Australia

Biochar Pyrolyzed biomass to create

charcoal

Demonstrated on wide variety of PFAS

Limited effectiveness on short-chain PFAS

Competitive sorption an issue

Requires disposal/destruction of media

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PAC+Additives* Ex-Situ Adsorption

Evaluated in Australia, U.S. and Germany

Passed PFAS contaminated water (1.8 mg/L) through two different columns, up to 100 pore volumes One column with activated carbon

One column with powder activated carbon and additives

Evaluated short- and long-chain PFAS

Removed shorter chain PFAS more effectively than activated carbon alone

* Rembind™. Data courtesy of Ziltek Pty Ltd.27

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Electrochemical Coagulation Electrical charges generate metal hydroxide floc

Floc is polar and sorbs to PFAS

Optimal energy, plate material, and pH control kinetics

Zinc anode shown to be best

Waste sludge disposal is needed

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Zn2+

Al3+

PFOA

ZnO/Zn0.70Al0.30(OH)2(CO3)0.15•xH2O

Figure courtesy of Bill DiGuiseppi, Jacobs

Use of direct current (DC) to degrade PFAS Electrode material (Boron-doped diamond, MMO, lead-dioxide etc.)

Major byproducts: Fluoride ions, shorter-chain PFAS, perchlorate

Limitations

Electrochemical Oxidation

29Reprinted with permission from Schaefer, et al., 2015. Electrochemical treatment of perfluorooctanoic

acid (PFOA) and perfluorooctane sulfonic acid (PFOS) in groundwater impacted by aqueous film forming

foams (AFFFs). Jour. Haz. Materials., 295:170-175. Copyright 2015 Elsevier.

Source: Schaefer et al. 2015

Oxidation/Reduction Approaches Activated Persulfate

High-temperature activation found to oxidize PFCAs, but not PFSA. Subject of current SERDP research.

Photolysis Typically in presence of catalyst

Geochemistry has profound effect

E-Beam Established, but not common, destructive technology for other

recalcitrant chemicals

Tested for PFAS in academic lab

Oxidizing/reducing chemical reactions

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Chemical Reduction

Zero Valent Metals Combination of sorption onto iron as well as

reduction via dehydrohalogenation

Ultraviolet light + sulfite Creates hydrated electrons, strong reducing

agents that react with carboxylates and sulfonates

Could be used for concentrate destruction

Vitamin B12 with titanium citrate Limited bench tests

Primarily attacks branched vs linear PFOS

Required high heat and pH in some cases

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Images courtesy of Timm Strathmann, Colorado School of Mines

HPLC Ret Time (min)

Before Treatment

HPLC Ret Time (min)

After 2nd Sulfite Add

Sonolysis (Ultrasound) Sound waves >19 kHz create

cavities in liquids

Cavities collapse at maximum radius creating extreme localized conditions High heat (50000K)

High pressure (1000 bar)

PFAS sorb to the cavity interface

Cavity collapses Cleaves bond between hydrophobic

and hydrophilic portions of molecules

32Figures courtesy of Michelle Crimi, Clarkson

Plasma Treatment

Uses electricity to convert water into mixture of highly reactive species OH•, O, H•, HO2

•, O2•‒, H2, O2, H2O2 and

aqueous electrons (e‒aq)

Plasma formed by means of electrical discharge between one high voltage and one groundwater within or contacting the water

Argon gas pumped through diffuser Produces bubble layer on surface that

concentrates PFAS

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Photos courtesy of Selma Mededovic, Clarkson

Stratton, G.R., et al. (2015). Chemical Engineering

Journal, 273: 543-550.

Stratton, G. R., et al., (2017). Environmental Science &

Technology 2017, 51(3):1643-1648.

Combined Remedy: Separate and Destroy

In situ precursor transformation with oxidation

Ex situ IX: regenerable resin

Plasma destruction of concentrated PFAS in liquid

34SERDP ER18-1306; ESTCP ER-5015

Figure courtesy of Michelle Crimi, Clarkson

Soil Separation/Washing

A handful of bench and pilot scale tests Torneman, 2017 – Two sites in Sweden

Ventia, 2018 – One site in Australia

Minimally documented, but available results are positive

Lower throughput for clay-rich soils

Treatment of multiple waste streams (water, sludge) required

Dry sieving may concentrate PFAS in limited volume fraction (i.e., clays and organic fines)

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Thermal Desorption for PFAS in Soil

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Bench scale information

Targeted for unsaturated zone AFFF source areas

Would require wet scrubber and scrubber water treatment (GAC)

Air discharge control would be needed

Initial Total

PFAS Conc.

(µg/kg)

% Decrease

in Total PFAS

Exposure

Temperature/

Time

Number of

PFAS

Analyzed

200 26 250°C 8 days 29

15140

99.4

300°C 4 days

350°C 2 days29

290

89.3-99.8

97.3->99.9*

99.8->99.9*

400°C 60 mins

550°C 50 mins

700°C 80 mins

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* >99.9% decreases are based on the limited analytical suite performed and based on decreases below the Limits of Detection

Data courtesy of William DiGuiseppi, Jacobs

PFAS Remediation Technologies: Takeaways

There are a lot of technologies with promise to treat PFAS

There are only a few that are considered field implemented Excavation and incineration or sorption/stabilization for soil

Pump and treat with GAC, membrane filtration, or ion exchange for water

Limited application approaches Thermal desorption or soil washing for soil

Injectable sorbents, coagulants for water

Developing technologies Destructive chemical treatment

Treatment trains (combinations of unit processes) should be considered

Treatability and pilot studies are the norm

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